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Sea-floor Spreading

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Vocabulary

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mid-ocean ridge :the longest chain of mountains in the world
sonar :the wave that scientists send down to see how long the mid-ocean ridge is
sea-floor spreading :the process the continually adds new material to the ocean floor
deep-ocean trench :an under water canyon
subduction :is the process which the ocean floor sinks beneath a deep-ocean trench and back into the mantle

outline

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Mapping the Mid-ocean Ridge

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• use sonar
  • longest chain of mountains in the world

Evidence from Sea-floor Spreading

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• evidence from molten material,magnetic strips and drilling samples

Subduction at Deep-open Trenches

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• the new oceanic crust is very hot

think of sea-floor spreading as a giant conveyor belt

Subduction and Earth's Ocean

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• the ocean floor is renewed about every 200 million years
  • the pacific ocean is shrinking
    • the Atlantic ocean is growing